Substance to be



1955 H. A. TOULMIN, JR Ra 24,080

' DRIED OR EVAPORATED FOOD PRQDUCTS), ESPECIALLY "ILK AND PROCESS OF MAKING IT Original Filed July 19. 1949 SUBSTANCE TO BE DEHYDRATED l4 l2\. FREEZING AND ICE DEHYmATm 16 l' cow wNc Nfl-R TE CONCENTRATE RAISED .TO

ROOM TEMPERATURE WARMED coNcENTRATE SPRAY DQYER INVENTOR HARRY A 'rouuam, JR.

DRY MATERIAL BY ATTORMYS Unite States Patent DRIED OR EVAPORATED FOOD PRODUCTS, ESPECIALLY MILK AND THE PROCESS OF MAKING IT Harry A. Toulmin, Jr., Dayton, Ohio, assignor to The Commonwealth Engineering Company of Ohio, Dayton, Ohio, a corporation of Ohio Original No. 2,656,276, dated October 20, 1953, Serial No. 105,590, July 19, 1949. Application for reissue August 3, 1954, Serial No. 447,696

6 Claims. (Cl. 99200) Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to a concentrated or dried food product and to a method of manufacturing it. Particularly, this invention relates to a dried or evaporated milk and the process of manufacturing it.

As is well known, the art of evaporating or drying milk and similar products is a large and commercially important industry. The advantages of evaporating or drying milk and similar products are many, and include greater ease of preserving the concentrated or dried product, ease of shipping or storing the same, and greater convenience to the consumer in transporting and storing the product.

However, as is equally well known, at the present time most of these products-and particularly milk, are characterized by a substantial change in taste after they have once been condensed or dried and then are rediluted to their original consistency for use. In connection with milk, this change in taste is particularly objectionable, and as a result, dried or evaporated milk has never come into popularity as a food arrived at by merely diluting the' concentrated dried product. Rather, the use of such products is mainly limited to use in cooking and in combination with other food products.

The particular object of the instant invention is the provision of an improved dried or evaporated milk product and a process of manufacturing it, such that the concentrate is characterized by undergoing substantially no change in taste, so it can be diluted to its original consistency by the mere addition of water used in place of fresh milk.

A still further object of this invention is the provision of a method of dehydrating foods, such as milk, by means of which the water can be extracted from the sub stance either in whole or in part, but without imparting to the product the cooked taste characteristic of most dried rnilks.

Another particular object of this invention is to provide a process for manufacturing dried or evaporated milk, and in which the combination of freezing and evaporating is employed for extracting the water from the milk.

These and other objects and advantages will become more apparent upon reference to the following specification, taken in connection with the accompanying drawing, wherein there is illustrated, diagrammatically, a process according to this invention.

Referring to the drawings generally, it will be seen that a substance to be dehydrated or concentrated is in troduced into the system, as at 10, and that the first stage that the substance goes through is a dehydration step by freezing. This is indicated by the rectangle at 12, and it will be seen that ice is extracted therefrom, as indicated by the arrow 14, and a concentrate is passed to the next step in the cycle, as indicated by the arrow at 16.

. 2' The aforementioned concentrate is then raised to room temperature, as indicated by the rectangle at 18, and then is passed, as shown by line20, to a blower 22 that blows the concentrate into a spray dryer 24. Within the spray Serial Number 36,547, filed July 1, 1948, and assignedto the same assignee as the instant application.

This process is characterized by reducing the temperature of the substance to be concentrated until ice crystals form therein, and then moving the ice crystals and the substance in counterflow relationship and extracting ice from the substance at the point of greatest dilution of the substance. In this manner the crystals that are formed are encouraged to grow to considerable size, so that the carry-out or occlusion of the substance on the ice crystals is reduced to a minimum. Further, by removing the ice from the substance at the point where the substance is most dilute, the carry-out is still further reduced, because the ice crystals are washed with the dilute substance. The bulk or major portion of the water, for example upv to of the amount present in the liquid foodstutfs, may be removed by freezing and removing the water in the form of ice.

The extraction of water in the manner described above, and more fully set forth in the above-identified application, is characterized in that the resulting concentrate can be rediluted to its original consistency and substantially no change in taste, texture, or aroma is detected. This is due to the fact that the substances which impart taste and odor are not extracted by the freezing process. Also, it is knownthat when a mixture, solution, or emulsion is reduced to the temperature at which ice crystals form, i

the said crystals will consist of pure water, assuming that the solute is water. Due to this fact, there are none of the solids, fats or oils of the substance being concentrated entrained in the ice, and therefore, all of the flavoring material, as well as the vitamins, remain in the concentrate, whether they comprise liquids or solids.

The concentration of substances according to the freezing process described above, however, has its limitations, because, as the concentration of the substance proceeds, it becomes thicker and more viscous, and it becomes more more diflicult to extract the ice crystals therefrom without carrying with them an unusually large amount of the concentrate. Thus, at a point, the extraction of water from a substance by freezing and moving the ice crystals in counterflow with the substance, becomes impractical.

In. connection with milk, with which this invention is particularly concerned, it is possible to extract water from the milk at least to the point that the resulting concentrate is the equivalent of commercial condensed milk. Considering whole milk, this has about eighty-seven per cent Water, and skimmed milk has a somewhat higher percentage, because a substantial amount of fat is removed from whole milk to arrive at skimmed milk. For the purpose of this invention, milk can be considered to be either whole or skimmed milk, and when this substance is reduced to a condensed state by a freezing and dehydration process as set forth above, the amount of water therein is somewhat between twenty-five and twenty-seven per cent. This limit of concentration is determined by Reissued Oct. 25, 1955 to a much higher'degree.

Dried milk, as contrasted to condensed or evaporated milk, must have the water extracted therefrom until the percentage of moisture is somewhere betweentwo and five per cent, and therefore, in order to arrive at a highly concentrated or dried product, further steps must be carried out on the milk following the dehydration thereof by freezing, as explained above.

According to this invention, the concentrate which flows from the freezing and dehydration process, and which is naturally quite cold and contains ice crystals, is first raised at least to room temperature, thereby melting the ice, At this temperature, no deterioration of the product obtains, and none of the aforementioned substances therein which impart flavor and odor to it will pass therefrom. The warmed concentrate is then passed to a spray drier and therein undergoes a process during which the remaining amount of moisture which it is desired to extract from the concentrate is removed.

Within the spray drier the concentrate is atomized, by spray wheels, discs, cups, nozzles,-jets, or other devices well known in the spray drying art, which will produce a fine mist of the material. Hot clean gas, such as air, is moved through the finely atomized spray and transmits heat to the individual particles of the spray, thereby evaporating the moisture therefrom and leaving behind the solids as a powder floating in the gas steam.

The powder is removed from the drier according to any of several methods, and any powder carried out by the stream of hot gases can be recovered therefrom by centrifuging or screening. Preferably, the powder is removed from the drier as rapidly as it forms therein and is immediately chilled and packaged.

The spray drier may have the hot gases so directed therethrough that acentrifuging action is'had on the dry solids formed, thereby quickly separating them from the gas stream and leading to more efiicient operation of the system, as well as further insuring against change of taste of the product.

The rapid action of the spray drier, in combination with the concentration by freezing, results in a product characterized by substantially no change in flavor or odor when reconstituted-to its original dilution by the addition of the amount of water extracted.

The complete process according to this invention is, then, characterized in that the material to be concentrated is first subjected to a relatively slow freezing and dehydration step, and, thereafter to a relatively rapid evaporating step, so that the water is taken out by a combination of freezing it into the form of ice crystals and by evaporating the remainder into the form of water vapor.

The method according to my invention has great commercial significance" in that it is a continuous process, and the substance being concentrated can be fed continuously into one end of the system and the dried or concentrated product extracted continuously from the other end. By avoiding batch treatment, a more uniform product is obtained, and favorable commercial practices can be observed in operating the plant.

It will be evident thatwhile this invention is particularly concerned with the dehydration of milk, it is equally adaptable to many other substances, such as fruit and vegetable juices which it is desired to reduce to a concentrated form for ease of shipping and preserving.

It will be understood that I do not wish to be limited to the exact proportions, ratios, and other factors specifically set forth in the foregoing description and the accompanying drawing, but desire to comprehend such changes thereof as may be further desirable to adapt my invention to different conditions and usages.

I claim:

1. A process of concentrating liquid foodstufis which may be reconstituted without substantial change in taste comprising reducing the temperature of the liquid food stuif in successive stages to form ice crystals therein which are substantially pure water, moving the resultant partially frozen concentrate continuously in counterflow relationship to the flow of the ice crystals formed, removing a major portion of said ice crystals from the liquid food-' I stufi being concentrated at the point where the liquid foodstuff is most diluted, removing the concentrate and a portion of the ice crystals from the reduced temperature stages when extraction of the ice from the concentrate without carry-out of the concentrate becomes diflicult, elevating the temperature of the concentrate removed to thaw the ice crystals therein, and rapidly evaporating the resultant concentrate to a water content of the desired value.

2. A continuous process of concentrating liquid foodstuffs which may be reconstituted without substantial change in taste comprising reducing the temperature of the liquid foodstuff in successive stages to form ice crystals therein which are substantially pure water, moving the resultant partially frozen concentrate substantially in counterflow relationship to the flow of the ice crystals formed, removing a major portion of the ice crystals from the liquid foodstuff being concentrated at the point where the liquid foodstutf is most diluted, removing the concentrate and a portion of the ice crystals from the reduced temperature stages when extraction of the ice from the concentrate without carryout of the concentrate becomes difficult, elevating the temperature of the concentrate to thaw the ice crystals therein, and evaporating the resultant concentrate under accelerated conditions to a water a portion of the ice crystals from the reduced temperature stages when extraction of the ice from the concentrate without carry-out of the concentrate becomes difiicult, elevating the temperature of the concentrate to thaw the ice crystals therein, and rapidly evaporating the resultant concentrate by subjecting the same to spray drying to produce a product having the desired moisture content.

4. A process of concentrating milk to produce a dehydrated product which may be reconstituted without substantial change in taste comprising reducing the temperature of the milk in successive stages to form ice' crystals therein which are substantially pure water, moving the resultant partially frozen milk concentrate continuously in counterflow relationship to the flow of the ice crystals formed, removing a major portionof said ice crystals from the milk being concentrated at the point where the milk is most diluted, removing the concentrate and a portion of theice crystals from the reduced temperature stages when extraction of the ice from the concentrate without carry-out of the concentrate becomes difiicult, elevating the temperature of the concentrate to thaw the ice crystals therein, and rapidly evaporating the resultant milk concentrate to a water content of the desired value.

5. A dehydrated milk product characterized by having the taste of fresh milk when reconstituted to its initial 6. A process of concentrating liquid foodstufis which may be reconstituted without substantial change in taste comprising reducing the temperature of'the liquid foods'tufi by successive stages to form ice crystals therein which are substantially pure water, moving the resultant partially frozen concentrate continuously therealong as the ice crystals are formed, removing a major portion of the ice crystals from the liquid foodstufi being concentrated at the point where the liquid foodstufi is most diluted, further reducing the temperature of the partially concentrated liquid foodstufl in a subsequent stage, removing a portion of the ice crystals therefrom and returning them to the initial low temperature stage, removing the resulting concentrate containing some ice crystals when extraction of the ice without carry-out of the concentrate becomes diflicult, elevating the temperature of the concentrate to thaw the ice crystals thereim and rapidly evaporating the resultant'concentrate by subjecting the same v to spray drying to produce a product having the desired 7 moisture content.

References Cited in the file of this patent or the original patent UNITED STATES PATENTS- 163,182 Gilmore May 11, 1875 1 \523,677 McIntyre July 31, 1894 723,152 Gurber Mar. 17, 1903 761,387 Monti May. 31, 1904 919,616 Monti Apr. 27, 1909 994,555 Alexander June 6, 1911 1,167,006 Monti Jan. '4, 1916 1,211,361 Sheehan Jan. 2, 1917 1,562,309 Dickerson Nov. 17, 1925 1,576,137 Johnson Mar. 9, 1926 1,738,275 Baker Dec. 3, 1929 2,248,634 Krause July 8, 1941 2,440,676 Dunkley May 4, 1948 

